Our civilization has not collapsed since Shakespeare. Ancient Egypt's did c. 1200 BC and never exactly recovered in terms of literacy though remnants remained

Our civilization has not collapsed since Shakespeare. Ancient Egypt's did c. 1200 BC and never exactly recovered in terms of literacy though remnants remained into early Roman times. Then it was conquered by the Greeks. Mesopotamia was even more completely buried and forgotten. A few names in the Bible, nothing more of the history survived until rediscovered in modern times. Around 400 BC, Xenophon returning from his campaign against the Persians, marched past the ruins of a great city. He was impressed with the size of it. The walls on stone foundations 20 ft tall! They're still there today, more or less. Perhaps the Medes had built it, according to the locals. Not much was known of the Medes, to the Greeks. It may have been quite ancient. Xenophon did not know that it was Nineveh, the capital of Assyria, last of the great Mesopotamian empires. It had been destroyed some 200 years before in the final war between Babylon and Assyria. The Mesopotamian cultural-political system sort of fell apart after. The languages of administration and history stopped being used. Written records ceased. The Persians came to rule the area. Only two hundred years and already forgotten.